Poly(arylene sulfide)s are crystalline engineering thermoplastics with high melting temperatures, typically on the order of 285° C., and are characterized by low flammability, high modulus, and excellent chemical resistance to aggressive chemicals and solvents. However, their glass transition temperatures are very low, typically as low as 85° C.; as a consequence, heat distortion temperatures are low in the in the absence of reinforcement with fillers such as glass fiber. In addition, poly(arylene sulfide)s are very brittle, as evidenced by a tensile elongation for polyphenylene sulfide usually no greater than about 2.5% and frequently below 1%.
Siloxane polyetherimides are a widely used class of thermoplastic engineering resins characterized by excellent hydrolytic stability, dimensional stability, toughness, heat resistance, and dielectric properties. However, they are deficient in certain other properties such as solvent resistance and flow in comparison with crystalline materials.
It might be expected that blends of poly(arylene sulfide)s and polysiloxane polyetherimide copolymers could be prepared which would have such properties as high solvent resistance, high heat distortion temperature, good ductility, and resistance to flammability. However, blends of this type are incompatible and undergo phase separation and delamination, as a result of little or no phase interaction between the two phases. Molded parts made from such blends are typically characterized by low tensile elongation and insufficient impact strength.
A need exists for blends of poly(arylene sulfide)s and polysiloxane polyetherimide copolymers having a combination of high tensile elongation and high Notched Izod impact properties.